For many years mixing of substances such as gases, liquids, solids or a combination of two or more of these substances was accomplished by mechanically driven mixers. These types of devices which are complex in structure and require many mechanical parts are often expensive, and difficult to operate and keep in good repair. Additionally, they often require a greater amount of space in which to operate, and occasionally have to be operated on a non-continuous basis. They tend to be slow in operation, in general are not as precise as one would desire, and occasionally foul when handling difficult to mix materials. Other problems that occur are loss of materials being mixed and problems created by high shear forces.
It should also be kept in mind that mechanical systems are not closed systems since they require frequent maintenance and repair. They also require a large capital investment particularly in certain environments. It also should be noted that they require slower mixing times and need a high energy source to operate at any reasonable speed.
As a result, there has been recent development activity in static type mixers where the actual mixing structure is motionless and the materials to be mixed are passed over or through a structure whereby they are intermixed.
The various types of static mixers which have been developed leave room for improvement. They are often expensive to manufacture and operate. They utilize complex and tortuous paths which provide many baffles or surfaces against which the substances to be mixed are directed which can interfere with the most desirable uniform type of mixing process and create problems such as fouling, clogging or hang-up of materials. Examples of known systems are present in U.S. Pat. Nos. 3,916,504; 3,583,678; 3,785,620; 3,358,749; 3,404,869; 3,286,992 and 3,652,061. These references all disclose various types of static mixing devices and they rely upon various baffle type structures to buffet and change direction of fluid flow rather quickly. The result, as stated above, is a system whereby for all occasions the most consistent type of flow pattern does not result. Therefore, while these types of static mixers are an obvious improvement over the mechanical type of mixing devices where the mixer moves in contrast to the mediums being mixed, there is still room for further improvement in the operation and functioning of this type of mixer.